Iran will be allowed to conduct research and development (R&D) with uranium for advanced centrifuges during the first 10 years of a nuclear agreement with major powers, according to the text of the deal posted on the Russian foreign ministry website.

"Iran will continue to conduct enrichment R&D in a manner that does not accumulate enriched uranium," the text of the agreement said. "For 10 years and consistent with its enrichment R&D plan, Iran's enrichment R&D with uranium will only include IR-4, IR-5, IR-6 and IR-8 centrifuges.

"Mechanical testing on up to two single centrifuges for each type will be carried out only on the IR-2m, IR-4, IR-5, IR-6, IR-6s, IR-7 and IR-8."